Simulation-based interpretation of spacecraft particle sensor measurements

基于仿真的航天器粒子传感器测量结果解释

• 批准号: RGPIN-2018-04956
• 负责人: Marchand, Richard
• 金额: $ 2.48万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=712616
• 关键词: Simulation; based; interpretation; spacecraft; particle

Particle sensors such as Langmuir probes or particle imagers, are used in many satellites and laboratory plasma experiments to infer plasma parameters such as the density and temperature. In its simplest form a Langmuir probe consists of an electrode which can be biased to variable voltages, and from which the electric current can be measured. The collected current as a function of bias voltage, the so-called probe characteristic, can then be interpreted on the basis of theoretical or computational models, to yield local plasma parameters. Much work has been done on this topic over nearly a century. Many theoretical, and more recently, several computational models have been developed to describe the response of Langmuir probes in a plasma. In practice however, probe measurements are almost universally interpreted in terms of simplified analytic models capable of producing real time answers in operation mode. Unfortunately these interpretations are notoriously uncertain, with error bars that can be of order 100%. The reason for these large uncertainties comes from the use of idealised models in which only a fraction of the relevant physical processes are taken into account. For example, some models only consider a probe in a stationary unmagnetised plasma, others account for plasma flow but neglect ambient magnetic fields, yet others account for a magnetic field, but ignore plasma flow or other effects such as photoelectron or secondary electron emission. In essentially all cases, plasma is assumed to be spatially uniform, and the presence of nearby satellite or experimental objects and their geometry is ignored. A promising solution to this predicament is to interpret particle sensor measurements on the basis of detailed computer simulations capable of accounting for the multiphysics which characterises plasma-material interaction, while also accounting for the geometry in which measurements are made. This is unfortunately not possible in real time operation mode owing to the time and computational resources required to do such simulations. One practical solution to be explored and developed in this proposed research, is to construct a library or data base for each experiment or space mission to be supported, from which plasma parameters could be inferred using a suitable regression technique. Compared to current practice, the new approach would lead to significant improvements in the accuracy of inferred plasma parameters. The proposed research would concentrate on producing solution libraries for selected spacecraft and experiments, developing, and assessing different regression techniques. An expected outcome of this research is a change of paradigm in the interpretation of sensor measurements, which would then rely on detailed kinetic simulation results rather than on idealised analytic models. This proposal is based on many years of experience in satellite-environment modelling.

在许多卫星和实验室等离子体实验中使用粒子传感器，例如langmuir探针或粒子成像仪，以推断等离子体参数，例如密度和温度。以最简单的形式，langmuir探针由一个电极组成，该电极可能会偏向可变电压，并可以从中测量电流。然后可以根据理论或计算模型来解释收集的电流作为偏置电压的函数，即所谓的探针特征，以产生局部等离子体参数。近一个世纪以来，在这个主题上已经完成了许多工作。许多理论上以及最近开发了几种计算模型来描述等离子体中Langmuir探针的响应。但是，实际上，探针测量几乎是通过能够在操作模式下产生实时答案的简化分析模型来普遍解释的。不幸的是，这些解释是不确定的，错误栏可能是100％。这些大型不确定性的原因来自使用理想的模型，在这种模型中，仅考虑了相关物理过程的一小部分。例如，某些模型仅考虑固定的未磁化等离子体中的探针，而另一些模型则说明了血浆流量，但忽略了环境磁场，而另一些则说明了磁场，但忽略了等离子体流量或其他效果，例如光电子或二级电子发射。在本质上，假定血浆在空间上是均匀的，并且附近的卫星或实验物体的存在及其几何形状被忽略。这种困境的一个有希望的解决方案是根据能够考虑具有等离子材料相互作用的多物理学的详细计算机模拟来解释粒子传感器的测量值，同时还考虑了进行测量的几何形状。不幸的是，由于进行此类仿真所需的时间和计算资源，这是在实时操作模式中不可能的。在这项拟议的研究中需要探索和开发的一种实用解决方案是为每个实验或空间任务构建库或数据库，可以使用合适的回归技术从中推断出等离子体参数。与当前的实践相比，新方法将导致推断等离子参数的准确性显着提高。拟议的研究将集中于为选定的航天器和实验，开发和评估不同回归技术的解决方案库。这项研究的预期结果是在解释传感器测量结果中的范式变化，然后将依靠详细的动力学仿真结果，而不是理想化的分析模型。该提议基于卫星环境建模的多年经验。